CompuServe Messages

James, the Amiga uses floppy drives with a fixed 'speed' of 300 rpm (880K). To my knowledge only the Apple Macintosh uses 'varispeed' disk drives which means the rotation speed is adjusted as the head moves towards the hub or the rim of the disk. This is the reason the Amiga is unable (except maybe for same hardware/software hacks) to read or write Apple Macintosh format floppy disks. On the Amiga, each track (cylinder) has the same number of sectors, i.e. no matter which track is read/written to it has a certain number of tracks which are read/written in a certain time. As the diameter near the hub is much smaller than at the rim an outer sector has more room (length) for its data than an inner sector. Macintosh format sectors have all the same length so there are more sectors on the outer tracks than on the inner tracks. At the same rotation speed, an outer track would have to transmit its data at another frequency than an inner track, thus the rotation speed is adjusted. The philosophy is clear: data safety! If a disk stores data safely in an outer sector it may not do so on an inner sector as the sector contains much less magnetic particles for the same amount of data. The Macintosh format has about the same amount of magnetic particles per sector on the inner tracks as on the outer tracks so risk of data loss (which normally occurs first on inner tracks) is reduced.